1. Field of the Invention
The present invention relates to a lithium metal polymer secondary battery and a method of producing the same, and more particularly, to an anode for a lithium metal polymer secondary battery comprising a patterned anodic current collector and a method of preparing the same.
2. Description of the Related Art
As the IT (Information Technology) industry advances, demand for small-sized, thin and light-weight electronic devices rapidly increases. One outstanding change resulting from the development of technology is in the field of office automation, where desktop-type computers are rapidly being substituted by small-sized and light-weight devices such as portable notebook PCs. Also, portable electronic devices, such as cellular phones, are being continuously minimized with complicated and diversified functions.
Thus, high performance lithium secondary batteries for supplying power to the above devices are also required. Currently, one of the lithium secondary batteries most broadly applied to small-sized IT devices is a lithium ion battery (LIB). An LIB can be more easily reduced in size and weight than a conventional Pb storage battery or a Ni—Cd battery, and has a high energy density.
The LIB uses as an anode a carbon-based material having a chemical potential similar to that of metal lithium upon the intercalation/deintercalation of lithium ions. A transition metal oxide such as lithium cobalt oxide (LiCoO2) having a potential 3-4.5 V higher than Lithium is used as a cathode. A liquid electrolyte/separator system is used as an electrolyte.
However, conventional LIBs have limited designs that effectively prevent leakage of a liquid electrolyte and it is well-documented that their performance is limited due to a fundamental limitation in material. Also, the production costs of LIBs are high and it is difficult to obtain a large capacity.
A lithium metal polymer battery (LMPB) has been developed to solve the problems of the conventional LIB and to provide superior performance. The LMPB includes metal lithium rather than the carbon-based material as an anode and a transition metal oxide having an improved capacity compared to the cathode material used as a cathode in the LIB. In particular, a polymer electrolyte is used instead of the conventional liquid electrolyte/separator system, and thus the LMPB has better stability than the LIB and can have various designs and be made larger.
However, even though the LMPB is spotlighted as a future power source, it has poor cycle properties and a short lifespan. A short circuit is caused due to the growth of lithium dendrite on the surface of a lithium anode when charging and cycling performance is degraded due to the presence of an irreversible reaction. Further, lithium clusters or particles released from the anode surface when discharging adversely affect stability. In addition, due to the formation of lithium dendrite, the thickness of the lithium anode changes, thereby causing expansion, shrinkage or deformation of a cell, which adversely affects the stability and lifespan of a battery.
To solve the above problems, research into preventing the formation of lithium dendrite and direct contact between a lithium anode and an electrolyte through surface modification of the lithium anode has been conducted (for example, U.S. Pat. No. 5,314,765 and U.S. Pat. No. 6,432,584 B1). Such examples somewhat reduce the formation of lithium dendrite. However, as long as the fundamental requirements for the formation of the lithium dendrite is not removed, volumetric deformation caused by expanding and shrinking of a cell due to a change in the thickness of the anode cannot be controlled. In particular, as the capacity or area of a cell increases, this problem becomes more serious.